The transforming thermal performance of residential buildings in the lower Himalayan cold climatic region

Residential buildings of lower Himalayan region have transitioned from vernacular construction systems involving wood and stone masonry to reinforced concrete & brick masonry during the medieval period and industrially manufactured materials and technologies in the contemporary times. This paper intends to evaluate the thermal performance of residential buildings of this region representing the three different time periods through real time field measurements. This paper adopts a three step approach involving, a reconnaissance survey and documentation of 100 houses, long-term coarse-grain indoor-outdoor environmental measurements for one-year in 10 houses and a short-term fine-grain thermal performance measurements and thermography studies in 4 houses during winter. With heating discomfort hours of 1104 hrs, passive adaptivity index of 0.28, and time lag, damping and heat loss of 3 hrs, 68 % and 1.1 W/m² respectively during winter, the vernacular buildings exhibited effective thermal performance. The medieval buildings showed a dip in thermal performance with higher heating discomfort hours (1355 hrs), higher passive adaptivity index (0.61) and higher heat loss (3.2 W/m²) during winter. However, the contemporary buildings deliver comparable thermal performance with that of vernacular buildings. This study intends to serve as a baseline for residential building thermal performance in cold climates of lower Himalayan region. With medieval buildings representing about 85 % of building stock in this region, the study highlights the potential energy benefits through performance retrofit of this building type.